1. Field of the Invention
The present invention relates to a position controller for a removable optical element which is moved onto and removed from a photographing optical axis in accordance with switching between a ready-to-photograph state and an accommodated state.
2. Description of the Related Art
A configuration in which a removable optical element, provided as part of a photographing optical system, which is movable in a plane orthogonal to an optical axis of the photographing optical system and is moved from a position on the photographing optical axis to a removed position radially away from the optical axis of the photographing optical system is known in the art as a lens-barrel (photographing lens) miniaturization technique, specifically as a technique that contributes to the reduction in thickness of a retractable lens barrel in an optical axis direction in a lens barrel accommodated state (fully retracted state) in which no pictures are taken.
In a retractable photographing lens disclosed in Japanese Unexamined Patent Publication No. 2003-315861 is provided, in a removable lens group support frame (20) movable in the optical axis direction of the photographing lens, with a removable lens frame (21) which holds a removable lens group and is rotatable (swingable) about a rotational shaft parallel to the photographing optical axis. When the photographing lens moves from a ready-to-photograph state to the lens barrel accommodated state, a rearward movement of the removable lens group support frame (20) in the optical axis direction firstly causes the position-control cam bar (11a) of the CCD frame (11) to come into contact with the position-control projection (21f) of the removable lens frame (21), and subsequently causes the position-control cam bar (11a) to press and rotate the removable lens frame (21) in a direction away from the photographing optical axis.
A retractable photographing lens disclosed in Japanese Unexamined Patent Publication No. 2008-170650 is configured to allow a positional adjustment of a third lens group (23) with respect to a shutter frame (9) in an optical axis direction when the third lens group (23) that serves as a retractable optical element is driven to retract from a photographing optical path. This photographing lens is provided with a rotational drive member (35) which is fitted on the pivotally-supporting boss (10a) of the third lens group frame (10) to be movable in the optical axis direction relative to the pivotally-supporting boss (10a) and to rotate with the pivotally-support boss (10a), and the rotational drive member (35) is pressed by an end-face cam (14) to rotate the third lens group frame (10) about the support shaft (52) via a rotational drive member (35) when the third lens group frame (10) is driven to retract to the retracted position.
A retractable photographing lens disclosed in Japanese Unexamined Patent Publication No. 2007-163961 is configured to allow the third lens group (L3), which is provided as a retractable optical element, to additionally perform an anti-shake operation (image shake correcting operation/image stabilizing operation). In this photographing lens, an oscillating member (17) is supported to be movable in a plane orthogonal to an optical axis relative to a fixed member (16) provided in the third lens group barrel (15), and an image-stabilizing optical system holding member (19) is rotatably supported by the oscillating member (17) thereon. In a ready-to-photograph state, an image-stabilizing operation is performed to correct image shake by driving the oscillating member (17) using a voice coil motor (18). When the photographing lens moves to the lens barrel accommodated state, a movement of the third lens group barrel (15) in the optical axis direction causes a driving member (4a) of a CCD mount (4) to come into contact with a contact portion (19b) of the image-stabilizing optical system holding portion (19) so as to press and rotate the image-stabilizing optical system holding portion (19) in a direction radially away from the optical axis from a position thereon.
It is desirable for the removable optical element removing operation to be performed efficiently with high precision with a structure which is as compact as possible. In a photographing lens like the photographing lenses disclosed in Japanese Unexamined Patent Publication Nos. 2003-315861, 2008-170650 and 2007-163961, in which the removable optical element removing operation is performed by translating a linear moving force of a moving member (which is adopted to perform the retracting operation of a photographing optical system) in an optical axis direction into a rotational force by a cam mechanism, the drive efficiency of the retracting operation (the amount of removal movement of the removable optical element per unit of linear movement of the moving member) can be set by the determining the profile of a cam surface of the cam mechanism.
However, in the structure like that disclosed in Japanese Unexamined Patent Publication No. 2007-163961 in which a removable optical element holding member (the image-stabilizing optical element holding member 19) is driven in a plane orthogonal to an optical axis for a purpose (i.e., image stabilization) irrelevant to the removable optical element removing operation, an anti-shake operation (vibration isolating operation/image stabilizing operation) causes the point of contact of the removable optical element holding member with a cam (the driving portion 4a) made for the removal driving to vary, which may deteriorate the accuracy of the removable optical element removing operation. To prevent this problem from occurring, countermeasures are required such as performing the lens barrel retracting operation after holding the holding member for the removable optical element at a predetermined position in a plane orthogonal to the optical axis. However, such a countermeasure tends to increase the size of the removal drive mechanism for the removable optical element, complicates the structure thereof and requires much time and trouble to adjust to the removal drive mechanism. In addition, even in the case where the removable optical element holding member is moved for any other purpose than image shake correction (shake reduction/image stabilization), if an adjustment is made to the position of the removable optical element in the optical axis direction (e.g., the position of the axis of the rotational member which holds the removable optical element) during the manufacturing stage or when a similar adjustment is carried out, the relative position between the holding member for the removable optical element and the cam mechanism varies, which requires a similar countermeasure. Additionally, in the case where the removable optical element is held on a holding member which can move in a plane orthogonal to the optical axis or the position of which is adjustable in this orthogonal plane, it is difficult to construct a compact removal drive mechanism for the removal optical element while preventing this mechanism from interfering with the aforementioned holding member.